ABSTRACT

The study evaluated the effect of dietary selenium (Se) and zinc (Zn) on growth, physiological responses, organ development, and laying performance of Shaver Brown pullet chickens using 180 day old chicks. The birds were assigned to four treatments (T₁ - T₄) (45/group, 15/replicate) in a Completely Randomized Design (CRD). Control group (T₁) received basal diet while T₂, T₃, and T₄ received diet supplemented with 0.3 mg Se, 120 mg Zn, and 0.3 mg Se + 120 mg Zn, respectively. The birds were reared on deep litter floor from 0 – 20 weeks of age (WOA), and in individual layer cages from 21 WOA. Birds were fed chicks mash containing 19.65 % CP and 2985 Kcal ME/kg from 0 – 8 WOA, growers mash ;16.85 % CP and 2954 Kcal ME/kg from 9 – 20 WOA ad libitum and layers mash;17.25 % CP and 2965 Kcal ME/kg at 125 g/bird/day from 21 WOA. Water was provided ad libitum throughout the study period. Parameters evaluated were growth performance, haematological and serum biochemical indices, tissue oxidative and antioxidant profiles, follicular dynamics and histomorphology, short-term laying performance and egg quality indices. Data were analyzed using one way analysis of variance in a CRD. Results showed significant treatment effects on growth performance, daily feed intake, and feed conversion ratio; relative organ weight, haematological, and serum biochemical indices, tissue oxidative and antioxidant profiles, reproductive organ development, follicular dynamics and histomorphology, laying performance, and some egg quality parameters. The final body weight, total weight gain, and daily weight gain were significantly lower (p<0.05) in birds fed zinc when compared with other treatments. Feed intake was significantly higher in T₁ (67.18 ± 0.19 g) compared with T₃ (65.48 ± 0.39g) and T₄ (65.81 ± 0.50 g) but similar between T₁ and T₂ while feed conversion ratio was significantly higher in T₃ (6.97 ± 0.04 g) compared with other treatments. At 8 and 20 WOA, PCV, Hb, and RBC; serum proteins, and liver enzymes (AST, ALT, and ALP) were higher in treated groups compared to control group. Whereas tissue malondaldehyde level (MDA, a measure of lipid peroxidation) was higher in the control group across the age periods, tissue antioxidants profile (CAT, GSH, and SOD) were either significantly higher (p < 0.05) in the treated groups or similar to those of control group. Weight of ovary was generally similar between treatments but oviduct weight and length were either higher in the treated groups or similar to the control. Follicular histomorphology showed more advanced development of ovarian follicles in treated groups compared to control group and hen day egg production was significantly higher in treated groups at weeks 33 – 37 and 38 – 42. In conclusion, dietary supplementation of organic Se and Zn reduced lipid peroxidation, and enhanced cellular antioxidant activity, reproductive organ development, laying performance, some growth parameters, and egg quality indices of pullet and layer chickens.